Transient control method and device for Variable valve timing system and Miller cycle engine

Abstract

The invention provides a transient control method and device for a variable valve timing system and a Miller cycle engine, and the method comprises the following steps: 1, judging whether an engine enters a transient working condition or not according to obtained engine operation state parameters; 2, determining target valve timing according to the rotating speed and the target load, and judging whether the inflation efficiency of the target valve timing is smaller than the inflation efficiency of the current valve timing or not; 3, keeping the current valve timing unchanged; and 4, adjusting valve timing to the target position, in the valve timing adjusting process, according to different operation states of the engine, coordinating the inflation efficiency change caused by the pressure of the intake manifold and the valve timing change, and achieving different torque output characteristics. The invention aims to at least solve the drivability problems of slow torque transient response and torque pit falling mentioned in the background technology.

Description

technical field [0001] The invention relates to the technical field of engines, in particular to variable valve timing control technology for Millerson cycle engines. Background technique [0002] As the market demands higher and higher fuel economy, Miller cycle technology is more and more widely used in gasoline engines. The Miller cycle is to control the intake air volume, the end-of-compression temperature and pressure of the gas in the cylinder by adjusting the closing time of the intake valve, thereby reducing the effective compression ratio of the engine, and obtaining a thermodynamic cycle mode in which the expansion ratio is greater than the effective compression ratio. Miller cycle engines are usually combined with high compression ratio technology, which can effectively improve the theoretical thermal efficiency of the engine and achieve a significant increase in fuel economy. [0003] Such as figure 1 As shown, in the process of pursuing the ultimate fuel consu...

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Problems solved by technology

Although this method can theoretically improve the transient response of the engine, it does not provide the switching control between steady-state VVT ​​control and transient VVT control, and cannot solve the aforementioned drivability problem of torque drop; and this method is to deal with two sets of VVT strategies. Need to add two sets of inflation models, two sets of torque models and two sets of software strategies for ignition angle control, which greatly increases the burden on the controller; it also involves two sets of VVT strategy calibration, two sets of ignition angle calibration, and two sets of inflation model calibration And the calibration of two sets of torque models, etc., need to increase a lot of calibration work

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